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src: large page support for macOS #28977

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7a698d4
src: large page support for macOS
devnexen Aug 5, 2019
59a2232
Fixing address copy handling.
devnexen Aug 8, 2019
0f7190f
Tweaks from feedback
devnexen Aug 20, 2019
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8 changes: 5 additions & 3 deletions configure.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1037,16 +1037,18 @@ def configure_node(o):
else:
o['variables']['node_use_dtrace'] = 'false'

if options.node_use_large_pages and not flavor in ('linux', 'freebsd'):
if options.node_use_large_pages and not flavor in ('linux', 'freebsd', 'mac'):
raise Exception(
'Large pages are supported only on Linux Systems.')
if options.node_use_large_pages and flavor in ('linux', 'freebsd'):
'Large pages are supported only on Linux, FreeBSD and MacOS Systems.')
if options.node_use_large_pages and flavor in ('linux', 'freebsd', 'mac'):
if options.shared or options.enable_static:
raise Exception(
'Large pages are supported only while creating node executable.')
if target_arch!="x64":
raise Exception(
'Large pages are supported only x64 platform.')
if flavor == 'mac':
info('macOS server with 32GB or more is recommended')
if flavor == 'linux':
# Example full version string: 2.6.32-696.28.1.el6.x86_64
FULL_KERNEL_VERSION=os.uname()[2]
Expand Down
2 changes: 1 addition & 1 deletion node.gyp
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Original file line number Diff line number Diff line change
Expand Up @@ -817,7 +817,7 @@
}],
],
}],
[ 'node_use_large_pages=="true" and OS in "linux freebsd"', {
[ 'node_use_large_pages=="true" and OS in "linux freebsd mac"', {
'defines': [ 'NODE_ENABLE_LARGE_CODE_PAGES=1' ],
# The current implementation of Large Pages is under Linux.
# Other implementations are possible but not currently supported.
Expand Down
98 changes: 77 additions & 21 deletions src/large_pages/node_large_page.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -30,6 +30,8 @@
#if defined(__FreeBSD__)
#include <sys/sysctl.h>
#include <sys/user.h>
#elif defined(__APPLE__)
#include <mach/vm_map.h>
#endif
#include <unistd.h> // readlink

Expand Down Expand Up @@ -212,6 +214,42 @@ static struct text_region FindNodeTextRegion() {
}
start += cursz;
}
#elif defined(__APPLE__)
struct text_region nregion;
nregion.found_text_region = false;
struct vm_region_submap_info_64 map;
mach_msg_type_number_t count = VM_REGION_SUBMAP_INFO_COUNT_64;
vm_address_t addr = 0UL;
vm_size_t size = 0;
natural_t depth = 1;

while (true) {
if (vm_region_recurse_64(mach_task_self(), &addr, &size, &depth,
reinterpret_cast<vm_region_info_64_t>(&map),
&count) != KERN_SUCCESS) {
break;
}

if (map.is_submap) {
depth++;
} else {
char* start = reinterpret_cast<char*>(hugepage_align_up(addr));
char* end = reinterpret_cast<char*>(hugepage_align_down(addr+size));
size_t esize = end - start;

if (end > start && (map.protection & VM_PROT_READ) != 0 &&
(map.protection & VM_PROT_EXECUTE) != 0) {
nregion.found_text_region = true;
nregion.from = start;
nregion.to = end;
nregion.total_hugepages = esize / hps;
break;
}

addr += size;
size = 0;
}
}
#endif
return nregion;
}
Expand Down Expand Up @@ -267,11 +305,15 @@ static bool IsSuperPagesEnabled() {
// 2: This function should not call any function(s) that might be moved.
// a. map a new area and copy the original code there
// b. mmap using the start address with MAP_FIXED so we get exactly
// the same virtual address
// the same virtual address (except on macOS).
// c. madvise with MADV_HUGE_PAGE
// d. If successful copy the code there and unmap the original region
int
#if !defined(__APPLE__)
__attribute__((__section__(".lpstub")))
#else
__attribute__((__section__("__TEXT,__lpstub")))
#endif
__attribute__((__aligned__(hps)))
__attribute__((__noinline__))
MoveTextRegionToLargePages(const text_region& r) {
Expand All @@ -289,6 +331,9 @@ MoveTextRegionToLargePages(const text_region& r) {
PrintSystemError(errno);
return -1;
}
OnScopeLeave munmap_on_return([nmem, size]() {
if (-1 == munmap(nmem, size)) PrintSystemError(errno);
});

memcpy(nmem, r.from, size);

Expand All @@ -302,7 +347,6 @@ MoveTextRegionToLargePages(const text_region& r) {
MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, -1 , 0);
if (tmem == MAP_FAILED) {
PrintSystemError(errno);
munmap(nmem, size);
return -1;
}

Expand All @@ -313,11 +357,6 @@ MoveTextRegionToLargePages(const text_region& r) {
if (ret == -1) {
PrintSystemError(errno);
}
ret = munmap(nmem, size);
if (ret == -1) {
PrintSystemError(errno);
}

return -1;
}
#elif defined(__FreeBSD__)
Expand All @@ -327,32 +366,46 @@ MoveTextRegionToLargePages(const text_region& r) {
MAP_ALIGNED_SUPER, -1 , 0);
if (tmem == MAP_FAILED) {
PrintSystemError(errno);
munmap(nmem, size);
return -1;
}
#endif

memcpy(start, nmem, size);
ret = mprotect(start, size, PROT_READ | PROT_EXEC);
#elif defined(__APPLE__)
// There is not enough room to reserve the mapping close
// to the region address so we content to give a hint
// without forcing the new address being closed to.
// We explicitally gives all permission since we plan
// to write into it.
tmem = mmap(start, size,
PROT_READ | PROT_WRITE | PROT_EXEC,
MAP_PRIVATE | MAP_ANONYMOUS,
VM_FLAGS_SUPERPAGE_SIZE_2MB, 0);
if (tmem == MAP_FAILED) {
PrintSystemError(errno);
return -1;
}
memcpy(tmem, nmem, size);
ret = mprotect(start, size, PROT_READ | PROT_WRITE | PROT_EXEC);
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Can you explain why this is necessary? It's already mapped rwx, isn't it?

Should the mmap() call include MAP_FIXED in its flags like it does on Linux and FreeBSD? If not, can you update the comment atop of this function?

Aside: since there are a lot of munmap(nmem, size) calls now, it'd be nice to DRY it:

nmem = mmap(...);
OnScopeLeave munmap_on_return([nmem, size] () {
  if (-1 == munmap(nmem, size)) PrintSystemError(errno);
});

I guess you lose the ability to return an error from MoveTextRegionToLargePages() on munmap() failure but that doesn't seem too bad, it's not really a fatal error and probably hypothetical to boot. You could simply abort on failure.

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@devnexen devnexen Aug 20, 2019 •
edited
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To answer your first question it is rx but will add a comment (note that s start address not the new address). Ok for the rest (including the info change in configure.py).

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Just to round out this discussion: using MAP_FIXED is not an option on macos? start is properly aligned, isn't it?

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start is indeed aligned like other platforms, MAP_FIXED failed on this platform though with 24MB close to the start address reservation attempt.

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Yeah, I'd have to go digging for the reason again but MAP_FIXED has long had problems with mmap for large page sizes on macos. Pretty sure the macos api docs recommend not to use it but if I recall correctly they don't really explain why.

if (ret == -1) {
PrintSystemError(errno);
ret = munmap(tmem, size);
if (ret == -1) {
PrintSystemError(errno);
}
ret = munmap(nmem, size);
if (ret == -1) {
PrintSystemError(errno);
}
return -1;
}
memcpy(start, tmem, size);
#else
memcpy(start, nmem, size);
#endif

// Release the old/temporary mapped region
ret = munmap(nmem, size);
ret = mprotect(start, size, PROT_READ | PROT_EXEC);
if (ret == -1) {
PrintSystemError(errno);
ret = munmap(tmem, size);
if (ret == -1) {
PrintSystemError(errno);
}
return -1;
}

return ret;
}

Expand All @@ -369,16 +422,19 @@ int MapStaticCodeToLargePages() {
return MoveTextRegionToLargePages(r);

return -1;
#elif defined(__FreeBSD__)
#elif defined(__FreeBSD__) || defined(__APPLE__)
return MoveTextRegionToLargePages(r);
#endif
}

bool IsLargePagesEnabled() {
#if defined(__linux__)
return IsTransparentHugePagesEnabled();
#else
#elif defined(__FreeBSD__)
return IsSuperPagesEnabled();
#elif defined(__APPLE__)
// pse-36 flag is present in recent mac x64 products.
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How recent is recent? Node.js supports macOS 10.11 and up.

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Then it is fine El Capitan is recent enough :)

return true;
#endif
}

Expand Down